Suppose you want to find 36.05\displaystyle \sqrt{{{36.05}}}.

The line tangent to the graph of y=x\displaystyle {y}=\sqrt{{{x}}} at x=36\displaystyle {x}={36} will have equation y=\displaystyle {y}=  

This means

x\displaystyle \sqrt{{{x}}}\approx  

Consequently

36.05\displaystyle \sqrt{{{36.05}}}\approx